Stop SQL::Abstract::Pg mutating inputs

[mohawk2]

Summary

Stop SQL::Abstract::Pg->select mutating its inputs on non-inner joins, by copying the input and shifting that. The current code shifts its inputs for non-inner join, removing the join-type modifier, which creates a fiendishly hard to track bug. Basically, this doesn't work:

my $sources = ['foo', [-left => 'bar', foo_id => 'id']];
is_deeply [ $sqlapg->select($sources) ], [ $sqlapg->select($sources) ];

Motivation

Subtly mutating function inputs leads to hard-to-track bugs

References

Sorry, none. Hopefully this summary plus the test modification (which now fails without the module change) makes clear the problem.

[kraih]

Thanks, resolved more efficiently.

[mohawk2]

And with no test to avoid regressions?